Autosomal recessive polycystic kidney disease (ARPKD) in a Nigerian newborn: a case report

Autosomal recessive polycystic kidney disease (ARPKD) is a rare genetic disorder but even rarer in Africans and it is one of the causes of nephropathies in childhood. Although isolated cases of adult PKD have been reported in Nigerians; to the best of our knowledge, this case is the first to be reported in the paediatric age group in Nigeria. A case of autosomal recessive polycystic kidney disease presenting with severe perinatal asphyxia and severe respiratory distressis here by presented. Fetal ultrasonography during the pregnancy missed the diagnosis. The difficulty in making diagnosis and management is discussed. Autopsy helped to unravel the diagnosis in this case report.


Introduction
Polycystic kidney disease can be inherited as an autosomal recessive (ARPKD) or autosomal dominant trait (ADPKD). Autosomal recessive polycystic kidney disease (ARPKD) is a rare genetic disorder but even rarer in Africans and it is one of the causes of nephropathies in childhood 1. It occurs with an estimated incidence of 1 in 20,000 live births [1]. Moreso, autosomal recessive polycystic kidney disease (ARPKD) very rarely exists in isolation; it often presents as Caroli's syndrome when Caroli disease is associated [2]. Both Caroli disease and Caroli syndrome are rare congenital disorders of the intrahepatic bile ducts characterized by dilatation of the intrahepatic biliary tree [3,4]. In Caroli syndrome, the malformations of small bile ducts and congenital hepatic fibrosis are often associated with autosomal recessive polycystic kidney disease (ARPKD). Caroli syndrome is generally inherited in an autosomal recessive manner similar to ARKPD [5][6][7]. The autosomal recessive pattern of inheritance is currently believed to be caused by a single gene with linkage to locus 6p21. This gene has been termed polycystic kidney and hepatic disease gene 1(PKHD 1) [8]. A frequency of 1 in 70 of carriers of the PKHD 1 gene exists in the general population [9].
The PKHD 1 gene manifests with widely varying severity of both the renal and the hepatic disease [10]. ARPKD is rare in Nigeria and the present case had many uncommon presentations hence the case presentation.

Patient and observation
A 9 hour old term male neonate was rushed into the neonatal unit of our facility with severe respiratory distress and gasping breathing.
He was delivered in a private hospital by emergency caesarean section on account of fetal distress and breech presentation. The details of immediate postnatal events and resuscitation measures could not be obtained because baby was brought in by maternal grandmother while the mother was still at the referral hospital. Bilateral renal agenesis, bilateral multicystic or polycystic kidneys and renal dysplasia area consequence of early-onset bladder outlet obstruction from either posterior urethral valves or urethral stenosis are lethal abnormalities in the neonatal period due to pulmonary hypoplasia [1][2][3][4]. Pulmonary hypoplasia is known to be common in the severe form of ARKPD [4,5]. The present case showed a severe form of ARKPD. During fetal development, the kidney is a major source of proline production which aids in the formation of collagen and mesenchyme in the lung. The absence of this vital protein that in part explain the severe pulmonary hypoplasia seen in polycystic kidney disease, renal agenesis or renal dysplasias [11,12]. The main diagnostic modality for neonatal renal cystic diseases is ultrasound imaging and most cases of neonatal renal cystic diseases (autosomal dominant PKD, autosomal recessive PKD and multicystic dysplastic PKD) are detected during prenatal USS screening [13].
This case however was not detected on USS underscoring the importance of improving diagnostic skills at the level of peripheral centres. Neonatal ARPKD can result in severe morbidity and grave prognosis. The factors that modulate gene expression of severity are yet to be defined and there remains therefore, a widespread pessimism about prognosis for ARPKD patients [13]. If the patient survives the neonatal period, current therapies include the management of arterial hypertension, dietary modifications such as a low protein diet, aggressive ventilatory support and renal replacement therapy (including pre-emptive nephrectomy, dialysis and transplantation) [14]. This may help minimize early infant mortality and give affected infants a favourable outcome.
Unfortunately, the patient in the present case died before any useful and significant intervention could be done.

Conclusion
Neonatal polycystic kidney disease may not be as rare as previously reported particularly in blacks. It is probably underdiagnosed especially where the appropriate skill for fetal ultrasonogram diagnosis needs improvement. Availability of good antenatal care and early ultrasound detection will improve the detection. Referral of suspected case before delivery to better equipped tertiary health facilities for early diagnosis and intervention can provide the advanced care that affected neonates require. This may also assist data collection on the prevalence, presentations and possible modalities of treatment that will invariably improve the prognosis and present neonatal health indices.